白鹤滩和乌东德库区蓄水前形变分析

Analysis of Deformation in Baihetan and Wudongde Reservoir Areas before Impounding

利用白鹤滩和乌东德库区2018~2019年两期最新地壳形变监测资料对两个库区在监视期的形变特征进行分析,其中水准和重力资料采用相对基准分析法,谷宽和跨断层测距资料采用投影面相对坐标分析法。结果表明:1)白鹤滩库区上游左岸中部存在16 km范围的沉降区,乌东德库区上游右岸水准支线所在地区隆升较大,两个库区其他地区均相对稳定,垂直形变量均小于5 mm;2)两个库区重力场变化基本平稳,无显著性异常变化,个别测点重力值变化较大是周围环境改变导致;3)两个库区4个谷宽网各点的相对坐标变化均不大,但4个谷宽网均显示相对收缩,量值在1~2 mm;4)两个库区6处跨断层场地中有5处比较稳定,监视期间断层无显著垂直活动和水平活动迹象,乌东德库区洛佐场地监视区断层两侧存在一定的差异性垂向运动并伴随水平向挤压运动。该结果可为水库蓄水后形变以及水库诱发地震的研究提供背景参考。

We analyze the deformation characteristics during the surveillance period using two newest crustal deformation monitoring data of Baihetan and Wudongde reservoir area in 2018-2019.We analyze the levelling and gravity data using the relative benchmark,and analyze the distance measurement data of valley width and cross-fault using the relative coordinates of the projection surface.The results show that:1)There is a settling zone with a range of 16 km in the central region of the left bank upstream of Baihetan reservoir area,and the levelling branch line of the right bank upstream of Wudongde reservoir area has a larger uplift.The rest of the two reservoir areas are relatively stable,and the vertical variables are less than 5 mm.2)The changes of gravity field in the two reservoir areas are basically stable,the gravity field has no significant abnormal changes,and the large changes in the gravity value of individual points are caused by the changes of the surrounding environment.3)The changes of the relative coordinates of each point of four valley width nets in the two reservoir areas are not large,but relative contraction is shown in four valley width nets,and the contraction value is 1-2 mm.4)There are five cross-fault sites in the two reservoir areas that are relatively stable,and there are no significant signs of vertical or horizontal activity during the monitoring period.There is a certain differential vertical movement accompanied by a horizontal compression movement on both sides of the fault in the surveillance area of Luozuo site in Wudongde reservoir area.The results can provide background information for the study of the deformation after reservoir impounding and the earthquakes induced by reservoirs.